DE2619863A1 - ELECTRIC HEATING ELEMENT - Google Patents

Description

PATENT AGENCY OFFICE

BERLIN - MUNICH

PATENT LAWYERS

DIPL-ING. W. MEfSSNER (BLN) DIPL.-ING. P. E. MEISSNER (MCHN) DIPL-ING. H.-J. PRESTING (BLN)

1 BERLIN 33, HERBERTSTR. 22nd

Your mark Your letter from Unser Mark Berlin, the 3rd i'lA: 18

405.006

EEEMEHT, INC. Troy, Oakland, Michigan USA

Electric heating element

The invention relates to a heating element for high temperature ovens in general and to an improved one Heating element for use in a radiant tube heater in high temperature ovens in particular "

The use of radiant tube heaters in heat treatment furnaces with high temperature are well known. Previously, the inside of a tubular part was heated with gas in order to heat up tubular part. This tubular part then radiates the heat outwards into the furnace. However, there were various difficulties and problems with the gas-heated radiant tube heaters, of which the the most important are the high costs and the low efficiency of gas heating.

The use of electrically heated element means of a radiant tube is also known. However, with the previous electric heating elements encountered various difficulties.

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BORO MONKS: TELEX: TELEGRAM: PHONE: BANK ACCOUNT: CHECK ACCOUNT: 8 MONKS 22 1-85844 INVENTION BERLIN BERLINER BANK AG. W. MEISSNER, BLN-W ST. ANNASTR. 11 INVEN d BERLIN 030/885 6037 BERLIN 31 122 82-109 TEL .: 089/223544 030/88823 82 3695716000

Usually, these electrical heating elements contain one Carrier with a hollow core and an electric heater. When current passes through the electrical heating device This heat radiates to the radiant tube, which in turn radiates heat into the furnace.

In previous electrical heating elements, the current return path was from the far end of the heating element (Inside of the oven) to the near end of the heating element (outside of the oven) within the hollow core of the carrier.

Yet another problem with the previous electrical heating elements is the aging of the electrical conductor. This Aging shows up as oxidation, pitting or corrosion of the conductor. Surrender as this condition progresses There are small holes in the conductors that grow larger and eventually cut off the conductors, which then become unusable and need to be replaced.

Yet another problem with the previous electrical heating elements is the lack of stability, i.e., sagging and stretching. The bending is the deviation from the original longitudinal axis and the expansion is the axial Extend, both of which occur during the use of heating elements at high temperature.

The invention solves the problems mentioned by a new electrical heating element, its entire electrical path lies outside the central core so that it generates useful heat for heating the tube or furnace.

The invention also includes electrical conductors of sufficiently large cross-section to prevent oxidation and corrosion

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sion to decrease. In addition, the invention enables the replacement of those conductors that corrode, or oxidize corrodesJTs-ind without affecting the whole electrical installation needs to be exchanged.

It is therefore an object of the invention to provide an improved electrical Heating element for a high-temperature furnace or the like, including a carrier with several thin, flat, non-conductive plates with several distributed openings and several non-conductive spacers, the smaller than the plates are to be specified, with a spacer between every two adjacent plates. Furthermore, the heating element contains an electrical heating device with a plurality of heaters, each of which by at least an opening in each plate leads out of the spacer. The ladder is held by the plates and the ends of the conductors are interconnected so that they have a single electrical path radially out of the spacer result out. The connections between the conductors hold the girder together.

Another object of the invention is to provide an electrical heating element in a radiant tube of a high temperature furnace Or the like. Specify with several axially distributed insulating washers, each of which is distributed several and parallel to the Disc axis arranged openings, several insulating spacers between adjacent discs and these from each other separating several conductive rods with long legs and a base indentation contains, the legs are inserted through aligned openings in each disc and axially and axially from the disc spacers to run radially outward from the spacer. The indentation of each rod lies over the boundary of the end plate out.

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Furthermore, each disk contains conductive devices that hold the rods, washers and spacers together and connects the rods together to form a single one result in a continuous electrical flow path through each rod and out of the spacers.

Still another object of the invention is an improved electrical heating element having a plurality of non-conductive elements longitudinally aligned spacers and a number of non-conductiveη plates, each with several axially extending holes, the plates in corresponding relationship by intermediate spacers in parallel Be kept spaced and the holes in the plates are axially aligned. Furthermore, several elongated ones are electrical conductive rods are provided, each of which is U-shaped is, and a kuirae base and parallel long legs each of which each rod is axially aligned through the aligned holes in the row of plates is and from the spacers, with the exception of the two rod legs, extends radially outward, so the free end of the leg of each rod leg puts the rods in a single electrical path and the two Rod legs can be connected to an electrical energy source.

These objects and advantages of the inventions, along with other objects and advantages gained in use, are used in conjunction with the. Drawings described in detail.
In the drawings is:

Figure 1 is a partial view of the electrical heating element according to

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of the invention inserted into a radiant tube;

FIG. 2 shows an enlargement of the front view of the heating element;

Figure 3 is an illustration of the heating element according to FIG Λ, viewed in the plane of arrows 3-3 with remote radiant tube;

Figure 4 is an illustration of the distal end of the heating element as seen in the plane of arrows 4-4 of the figure 1;

Figure 5 is an illustration of the front end of the heating element, seen in the plane of the arrows 5-5 of Figure 1; and

Figure 6 is a representation of the front end of the heating element according to the invention, seen in the plane of the arrows 6-6 of Figure 1.

The electrical heating element IO according to the invention is located as shown in FIG. 1, in a hollow tube 11 with a closed, distal end 12 and a flanged front end End 13, which is used for fastening in an oven. The tube 11 is preferably made of a heat-resistant alloy. Steel pipe can also be used in lower temperature furnaces. The support of the heating element after The invention includes several thin, flat, ceramic plates or discs 15 with two plates 16 and 17 at the front or first end of the device and penultimate and final panels 18 and 19 at the far end

Each plate is preferably identical and has one

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Central axis bore 2O ₁ which is surrounded by a circular groove 21 on each side of the plate, and has several openings running parallel to its axis, which are arranged in several rows, as FIG. 3 shows. There are two circular rows of openings 22 and 23 _y which are rounded off at 24 »These rows and the openings are arranged radially distributed accordingly and in a preferred embodiment, the openings 22 are angularly offset from the openings 23 to the area of the current-carrying conductor of the radiation pipe to be exposed immediately.

The support structure also contains several identical, non-conductive spacers 25 made of ceramic material, which are preferably hollow and open at both ends. The diameter of the spacers 25 corresponds to that of the circular ones Groove 21 in each panel and should be sufficiently smaller than that of panels 15 so that all of the openings 22 and 23 extend radially outward from the spacers 25. A spacer 25 is located between two adjacent ones Plates 15 · They thus serve to separate these plates from one another.

The electric heater according to the invention contains several electric conductors, which in a preferred embodiment are solid rods of circular cross-section, wherein the ladder or rods are hairpin or U-shaped. The "use of a rod with a circular cross-section results an optimal thickness-area ratio, which extends the service life compared to previous heating elements is because the rod thickness is susceptible to oxidation, pitting or corrosion, which would otherwise make the rod whole penetrates, diminishes.

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Each ladder or bar 30 includes two elongated ones parallel legs 31 and 32 through a base or an indentation are connected to one another. When making the support structure, the openings are in each Plate aligned and each rod leg is parallel to through the series of aligned openings the plate axes used. The rods are only inserted through the penultimate plate 18 with the indentation 33, which forms a connection between the legs 31 and 32 of each rod, and goes beyond the limits of the End or the penultimate plate 18 also. Thus, the rods pass through and between each plate the adjacent plates from the penultimate 18 through each plate 15 to the second plate 17. The distance between the Plates 17 and 18 determine the effective length of the heating element 10. Each plate supports and supports the rods 30 and the base or indentation 33 of each rod 30 the distant end of the structure.

At the distal end of the element 10, an additional support is provided which both supports and supports the assembly prevents electrical contact between the base 33 of the rod and the end 12 of the radiant tube. At a The preferred embodiment is a spacer 25 and the last plate 19 is used. A pin 35 'e.g. a A stainless steel pin with 18 parts of chromium and 8 parts of nickel is inserted inside the spacer 25. The pin has an opening at each end for receiving cotter pins 36. These and the stainless pin prevent that the penultimate plate 18 and the last plate 19 separate, and the spacer prevents this both plates can come close together.

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During the assembly of the element 10, the rods 30 through, the openings 22 and 23 of the penultimate plate 18 used. Then the support of the stainless steel pin 35j becomes the spacer 25 and the final plate 19 composed. Finally, the remaining support and panels 15 and 17 with the spacers 25 through aligned openings 22 and 23 in each Plate assembled.

For electrically connecting the free ends of the legs 31 and 32 of the rods and for the rest of the support of the Plates and spacers serves a special facility. All legs 31 and 32 of the rods 30 are in the Figures 2, 5 and 6 shown. You go through the openings in the second ceramic plate 17 through. Figure 5 shows a series of connecting rods therefrom Size and made of the same material as the conductive rods 30 attached to the free end of a leg 31 of a U-shaped Head are welded to the free end of one leg of another U-shaped conductor. The connection between the two Ends of the legs of the conductive rods are made with four legs of four different U-shaped rods, which, as Figure 5 shows, through the four leg ends 4-1 and 42 remain unconnected.

Then the first ceramic plate 16 and the position with the four leg ends 4-1, 4-2 extending therethrough is brought. A crossing rod 4-3 made of the same material as the connecting rods 4-0 and the ladder 30 are then connected to the both free leg ends 4-2 welded. This leaves the two leg ends 4-1 free from the connection, results but at the same time a continuous electrical path from a free leg end 4-1 at a distance through each U-shaped conductor and each connecting rod and crossing through it, this electrical path occurs at the other

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free leg end 4-1. All the electric way is therefore led radially outward from the spacer.

The rest of the carrier and the electrical circuit are explained in connection with FIGS. Preferably the distance between the two free ends 4-1 of the rod is reduced to a diameter suitable for the connection to the electrical power source is more suitable and at the same time connections of a greater thickness for the connections results. Furthermore, an additional carrier is to be provided for this first end of the heating element. Therefor two rods 4-5 will be made of the same material as the ladder JO but with a slightly larger diameter at 46 welded to the free leg ends 4-1. The top ends The 4-5 rod will be at 4-7 with the ends of the connecting rods 48 welded, which preferably consist of a stainless steel 35-15. These connecting rods 48 have one 1.55 mm in diameter. The connecting rods are through a first insulating block 50 with two holes 51 for receiving the connecting rod 48 and two additional vent holes 52 inserted therethrough. Are on the connecting rods 50 washers on both sides of the first insulating block 53 welded on. A suitable insulating block is, for example, a Marinite disc from John Mansville Conpany.

The connecting rods go through a second mainite block 55. The washers 56 are on the connecting rods 48 welded inside the second block 58.

The heating element according to the invention has been tested with the following result:

The insulating plates had a diameter of 123 mm and a thickness of 1.26 mm with 17 openings in the outer egg.

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he and 17 openings in the inner row. Then 17 TJ-shaped conductors were inserted and the whole thing was brought into a tube with an outer diameter of 15 * 2 mm. The effective heating length was 1060 mm. There were thermocouples inside and outside the tube. The energy was supplied with different voltages between 4-5 to 60 ToIt and currents of 30 to 45 Impere (the heating element is designed for 137 volts) «, The temperature of the tube was 1200 ⁰ C. During a part of the experiment over 24- Hours the temperature exceeded 1265 ° C. Similar experiments ran in a larger version with a lower current and the temperature on the outside of the tube exceeded 84-0 ⁰ C.

The special result of these tests was that no measurable sag (changes in relation to the longitudinal axis) and no measurable increase (change in axial length) occurred during the experiment. Although these attempts are not took place under actual operating conditions, the test result showed that the necessary operating conditions when heating a furnace to 1078 ° G can be achieved with the invention and no measurable sag or a Enlarging the electric heating element revealed.

However, many changes are within the scope of the Invention possible. While the use of U-shaped Rods that can easily be replaced individually if a rod is corroded can also be used with straight rods welded at both ends. In the same way it is depending on the atmosphere of the heat treatment furnace it is also possible to use the heating element without a radiant tube. Furthermore, need the spacers according to the invention not to be hollow and, unlike other arrangements for attaching the last plate 19 to the penultimate plate 18 serve.

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Summary:

The heating element for a high temperature furnace contains one Carrier and an electric heater. The carrier contains several thin, flat, non-conductive plates each with several distributed openings and several non-conductive spacers that are smaller than the plates, with one spacer between two adjacent ones Plates is located. The electrical heating device contains several long, preferably U-shaped, electrical ones Ladder with each leg extending radially outwardly from the spacer through an opening in each plate. the Conductors are held by the plates and run between them. The ends of the ladder are like this with each other connected to provide a single tortuous electrical path radially away from the spacers. The connections between the ladders hold the girder together «,

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Claims (15)

Patent claims: 1.! Electric heating element for a radiant tube furnace with high temperature or the like., characterized by a Carrier with thin, flat, non-conductive plates (15, 16, 17), each of which has several arranged in a distributed manner Openings (22) parallel to the plate axis and several non-conductive spacers (25) smaller than owns the plates, one of which is between two adjacent plates located, and by several elongated rigid electrical conductors (30), one of which each extending radially outwardly from and from the spacer through at least one opening in each plate the plates and is held between them, the ends (41,42) of the conductors being connected to one another in such a way that that the interconnected conductors radially follow a bound electrical path from the spacers on the outside and the ladder hold the carrier together. 2. Heating element according to claim 1, characterized in that the conductors (JO) two long connected by the base (33) Legs (31,32), each of which through an opening (22) in each plate (15 to 19) through 609846/0800 BORO MONKS: TELEX: TELEGRAM: PHONE: BANK ACCOUNT: CHECK ACCOUNT: 8 MONKS 22 1-85644 INVENTION BERLIN BERLINER BANK AG. W. MEISSNER, BLN-W ST. ANNASTR. 11 INVEN d BERLIN 030/885 80 37 BERLIN 31 122 82-109 TEL .: 089/22 35 * 4 030/886 23 82 3695716000 gellt and taking the bases of the ladder over the end plate and the connector at one end of the assembly form. 3. Heating element according to claim 1, characterized in that that the spacers (25) are aligned in the longitudinal direction on a common axis and the electrical Head (JO) run parallel to this axis. ¹ V. Heating element according to Claim 1, characterized in that the openings (22) in each plate lie in adjacent and spaced-apart rows. 5. Heating element according to claim 4, characterized in that the rows are circular and radially spaced and that the openings (22) are angled between two adjacent rows are staggered. 6. Heating element according to the preceding claims, characterized by a plurality of insulating washers arranged in an axially distributed manner (15 to 19) with someone at a distance and openings (22) arranged parallel to the disk axis and with several insulating spacers (25) between adjacent disks spaced from each other by a plurality of conductive rods (30), each of which has long legs (31,32) and base parts (33) and through aligned openings (22) in of each disc are inserted, axially from the disc-spacer assembly and radially from the spacers lead away and that the base parts (33) of each rod (30) is above the limit of the end plate, and through the Rods (30) holding the washers (15 to 19) and spacers (25) together and connecting the rods 609846/0800 Conductor (30) to obtain a continuous electrical Flow path through each rod. 7. Heating element according to claim 6, characterized in that the conductors contain a plurality of connecting rods (30), each of the free end of each pole leg (31> 32) with the free end of the leg of another rod and with two legs of other rods that connects remain free of connecting rod connection and serve for connection to a source of electrical energy. 8. Heating element according to the preceding claims, characterized by several hollow, non-conductive, lengthways aligned spacers (25), by a series of thin, flat, non-conductive plates (15 to 19) each with several axially extending openings (22) which are arranged in several rows in each plate, the plates being separated by spacers (25) are kept parallel and the openings are axially aligned by several elongated, electrical conductive rods (30) which are each ΙΓ-shaped and have a short base (33) and parallel elongated legs (31 j32), each leg axially through the aligned openings (22) is inserted in the plates and extends radially outward from the spacers, and by means for electrically connecting the free end of each leg bar (30) other than two legs of different rods with the free end of one leg of a different rod on one first end of the heating element (10) to bring the rods into a single electrical path, with the remainder two rod legs connected to each other, hold the spacers (25) and the plates (15 to 19) together. - 15 609846/0800 9. Heating element according to claims 8, characterized in that.die spacers (25) are of equal length and are located between adjacent plates (22). 10. Heating element according to claim 9 »characterized in that that the bases (33) of the rods (30) extend beyond the end of the plate and that each plate has an axial center - bore radially inside the spacer and a groove in each flat side of the plate to receive it of the end of each spacer 11. Heating element according to claim 10, characterized in that that another non-conductive plate, which is identical to the end plate, and another spacer for additionally supporting the heating element (10) and for isolating the bases (33) of the rods (30) from the radiant tube (11) are provided that the further plate is arranged away from the end plate and through an axial Pin is attached, which passes through the spacer and the axial center bore and the further plate, and that the axial pin is mounted inside the end plate and outside the further plate, 12. Heating element according to claim 1, characterized in that an additional non-conductive plate in a corresponding Distance from the end plate and attached to it is arranged axially away from the conductors to the Insulate the conductor against the jet pipe (11). 13. Heating element according to claim 6, characterized in that 'that an additional insulating plate at an axial distance from the arcuate portions of the conductive rods and isolate the conductive rods (30) from the jet pipe (11). 609846/0800 -16- 14. Heating element after. Claim. 8, characterized, that the openings (22) are rounded to block the heat from the rods to the radiant tube (11) to reduce. 15. Heating element according to claim. 8, characterized, that an additional non-conductive plate is attached to the end plate and axially spaced is to isolate the bases (33) of the rods (30) from the jet pipe (11) » Dipl.-Tag. P. E. Meissner Patent attorney 609846/0800 4t. Blank page